Design of Lead-Free and Stable Two-Dimensional Dion-JacobsonType Chalcogenide Perovskite A′La2B3S10 (A′ = Ba/Sr/Ca; B = Hf/Zr) with Optimal Band Gap, Strong Optical Absorption, and High Efficiency for Photovoltaics

Searching for energetic photovoltaic absorbers is a favorable solution to the current energy crisis. As a star material for solar cells, MAPbI(3) (MA = CH3NH3) has a suitable band gap, strong optical absorption, great defect tolerance, and high certified power conversion efficiency (PCE) up to 25.2%. However, the lead toxicity and poor long-term stability limit its application in photovoltaic devices. To break through these bottlenecks, we design two-dimensional (2D) Dion-Jacobson (DJ)-type (n = 3) chalcogenide perovskites A'La2B3S10 (A' = Ba, Sr, Ca; B = Hf, Zr), with optimal band gap, strong optical absorption, high carrier mobility, and excellent optoelectronic properties, based on the powerful first-principles and advanced HSE06 calculations. Especially, we find that, superior to MAPbI3, 2D A'La2B3S10 perovskites have the following several outstanding properties. (1) They are Pb-free and environmentally friendly. (2) The structural stability is better than that of MAPbI(3). (3) The direct band gap (similar to 1.33 eV of BaLa2Hf3S10), i.e., the optimal value of the SQ limit, is more suitable than that of MAPbI(3) (similar to 1.55 eV) with a 0.22 eV energy-loss spectrum. (4) The carrier mobility (1.8-2.6 x 10(3) cm(2) V-1 s(-1)) is larger than that of MAPbI(3) (similar to 37 cm(2) V-1 s(-1)). (5) The optical absorption (similar to 6 x 10(5) cm(-1)) in the visible range is three times stronger than that of MAPbI(3) (similar to 2 x 10(5) cm(-1)). (6) The estimated PCE (similar to 30.9% in BaLa2Hf3S10) is higher than that of MAPbI(3) (similar to 30%). These amazing characteristics indicate that 2D A'La2B3S10 perovskites are promising absorbers for photovoltaics.